In my copending application, Ser. No. 713,679 (now U.S. Pat. No. 4,091,948), there is disclosed a container and closure combination capable of sealing the container contents from the atmosphere with a "tight" seal. A "tight" seal is defined with reference to industry and governmental standards set forth in publications referred to. The seal is accomplished by the interaction of a resilient tapered sealing fin depending from the upper inner portion of the closure and a tapered sealing surface which forms the upper terminal surface of the container. The angle and configuration of the container sealing surface is disclosed as being within well-defined limits and the angle and configuration of the sealing fin is also well-defined.
The copending application also teaches that the closure and its projecting sealing fin may be molded as a single piece if desired.
The copending application also teaches that the container-closure combination may include a threaded connection between the parts, or a so-called "child-proof" combination comprising a well-known bayonet lock between the closure and container.
While a one-piece closure has certain advantages, I have found that the ease with which closures of my invention may be formed can be improved by molding the closure in two pieces. This not only permits the use of different materials for that portion of the closure carrying the sealing fin and the remainder of the closure but also simplifies the molding process itself. The first piece of the two-piece closure may comprise the element that attaches to the container either by screw threads or by the bayonet lock or by any other attachment means. The second element includes the panel that interfits into the top of the closure and the depending flexible sealing fin. Means are provided to assemble the two parts in a manner that requires only a friction fit as by interfitting ribs and grooves. Once the parts are snapped together, there is no likelihood that they will become accidentally separated.
It is particularly true that in closures for child-proof containers it is sometimes desirable to select a less resilient plastic material for the attachement portion of the cap than is required for the successful production of the flexible depending sealing fin. It is important that the sealing fin not only performs the sealing function but also serve as a spring to hold the bayonet lock in its closed position.